I keep getting a NullReference exception. works just fine in visual studio.

using System;

namespace Treehouse.CodeChallenges
{
    class Program
    {
        static void Main()
        {

            while (true)
            {
                Console.Write("Enter the number of times to print \"Yay!\": ");
                var entry = Console.ReadLine();
                if (entry.ToLower() == "quit")
                {
                    break;
                }

                var numberOfRepeats = int.Parse(entry);
                var n = 0;

                while (n < numberOfRepeats)
                {
                    Console.WriteLine("\"Yay!\"");
                    n++;
                }
                Console.ReadLine();
            }
        }
    }
}